Obtaining micro- and macro-rock properties with a calibrated rock deformation simulation

Abstract

A method for estimating a property of an earth formation includes: obtaining a sample of rock; scanning the sample to determine internal rock damage; measuring a deformation parameter of the sample; constructing a mathematical model of the sample that replicates the determined and measured internal rock damage distribution; simulating the one or more tests using the mathematical model; obtaining a rock deformation parameter using the one or more simulated tests corresponding to the measured rock deformation parameter; comparing the rock deformation parameter obtained from the one or more simulated tests to the corresponding measured rock deformation parameter; adjusting parameters of the mathematical model based upon the rock parameter obtained from simulation not being within a selected range of the measured rock parameter; and providing the mathematical model as a verified mathematical model based upon the rock parameter obtained from simulation being within a selected range of the measured rock parameter.

What is claimed is: 
     
       1. A method for performing an operation on an earth formation using an estimated property of the earth formation, the method comprising:
 obtaining a sample of rock from the earth formation; 
 scanning the sample with a volumetric imaging device to obtain a three-dimensional volume representation of the sample; 
 determining internal rock damage of the sample using the three-dimensional volume representation of the sample; 
 performing one or more tests on the sample using a rock test device; 
 measuring a deformation parameter of the sample using a deformation sensor; 
 constructing a mathematical model of the sample that replicates the determined and measured internal rock damage and damage distribution of the sample; 
 simulating the one or more tests using the mathematical model; 
 obtaining a rock deformation parameter using the one or more simulated tests corresponding to the measured rock deformation parameter; 
 comparing the rock deformation parameter obtained from the one or more simulated tests to the corresponding measured rock deformation parameter; 
 adjusting parameters of the mathematical model based upon the rock parameter obtained from simulation not being within a selected range of the measured rock parameter; 
 providing the mathematical model as a verified mathematical model based upon the rock parameter obtained from simulation being within a selected range of the measured rock parameter; 
 estimating an unconfined compressive strength (UCS) of the earth formation using the verified mathematical model; and 
 at least one of (a) pumping hydrocarbons from the earth formation using a pump and a controller at a flow rate determined by the estimated unconfined compressive strength (UCS) in order to avoid sand grains from being pumped with the hydrocarbons, and (b) pumping drilling fluid for drilling a borehole using drilling equipment, the drilling fluid having a weight that is selected using the estimated unconfined compressive strength (UCS) to avoid collapse of the borehole; 
 wherein the determining, constructing, obtaining a rock deformation parameter, comparing adjusting, providing, and estimating are performed using a processor. 
 
     
     
       2. The method according to  claim 1 , wherein obtaining a sample of rock comprises using a downhole coring tool. 
     
     
       3. The method according to  claim 1 , wherein the testing comprises at least one of non-destructive testing and destructive testing. 
     
     
       4. The method according to  claim 3 , wherein the destructive testing comprises multistage testing in which successive stages result in increasing damage. 
     
     
       5. The method according to  claim 1 , wherein the deformation sensor comprises at least one of a strain sensor, a size measuring sensor, and an acoustic transducer. 
     
     
       6. The method according to  claim 1 , wherein measuring comprises determining a location of damage using acoustic signals obtained from the acoustic transducer. 
     
     
       7. The method according to  claim 1 , wherein the mathematical model comprises a modified Mohr-Coulomb model having a term representing dilatation in an out-of-plane orientation. 
     
     
       8. The method according to  claim 1 , wherein the mathematical model comprises a three-dimensional mathematical model. 
     
     
       9. A system for performing an operation on an earth formation using an estimated property of the earth formation, the system comprising:
 a volumetric imaging device configured to scan a sample of rock form the earth formation to obtain a three-dimensional volume representation of the sample; 
 a rock test device configured to perform one or more tests on the sample; 
 a deformation sensor configured to measure deformation of the sample due to the one or more tests; 
 a memory having computer-readable instructions; 
 a processor for executing the computer-readable instructions, the computer-readable instructions comprising: 
 determining internal rock damage of the sample using the three-dimensional volume representation of the sample; 
 constructing a mathematical model of the sample that replicates the determined internal rock damage and damage distribution of the sample; 
 simulating the one or more tests using the mathematical model; 
 obtaining a rock deformation parameter using the one or more simulated tests corresponding to the measured rock deformation parameter; 
 comparing the rock deformation parameter obtained from the one or more simulated tests to the corresponding measured rock deformation parameter; 
 adjusting parameters of the mathematical model based upon the rock parameter obtained from simulation not being with a selected range of the measured rock parameter; 
 providing the mathematical model as a verified mathematical model based upon the rock parameter obtained from simulation being within a selected range of the measured rock parameter; and 
 estimating an unconfined compressive strength (UCS) of the earth formation using the verified mathematical model; 
 at least one of (a) a pump and controller configured to pump hydrocarbons from the earth formation at a flow rate determined by the estimated unconfined compressive strength (UCS) in order to avoid sand grains from being pumped with the hydrocarbons, and (b) drilling fluid for drilling a borehole using drilling equipment, the drilling fluid having a weight that is selected using the estimated unconfined compressive strength (UCS) to avoid collapse of the borehole. 
 
     
     
       10. The system according to  claim 9 , further comprising a downhole coring tool configured to extract a sample of rock from the earth formation. 
     
     
       11. The system according to  claim 9 , wherein the test equipment is configured to perform at least one of non-destructive testing and destructive testing. 
     
     
       12. The system according to  claim 9 , wherein the deformation sensor comprises at least one of a strain sensor, a size measuring sensor, and an acoustic transducer. 
     
     
       13. The system according to  claim 12 , wherein the computer readable instructions further comprise determining a location of damage using acoustic signals obtained from the acoustic transducer. 
     
     
       14. The system according to  claim 9 , wherein the mathematical model comprises a modified Mohr-Coulomb model having a term representing dilatation in an out-of-plane orientation.